Know More about Heat Exchanger

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Know More about Heat Exchanger

Posted On : Oct-18-2011 | seen (383) times | Article Word Count : 569 |

The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air.

A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, natural gas processing, and sewage treatment.
How does it Work
A heat exchanger utilizes the fact that heat transfer occurs when there is a difference in temperature.
In a heat exchanger, there is a cold stream and a hot stream. The two streams are separated by a thin, solid wall. The wall must be thin and conductive in order for heat exchange to occur. Yet the wall must be strong enough to withstand any pressure by fluid. Copper seems to be one of a common choice for construction
Flow Arrangement
There are two primary classifications of heat exchangers according to their flow arrangement. In parallel-flow heat exchangers, the two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side. In counter-flow heat exchangers the fluids enter the exchanger from opposite ends. The counter current design is most efficient.
Some ways to improve the performance of a heat exchanger:
• heat transfer area
• fluid flow velocity
• temperature gradient
There are a variety of designs and models of heat exchangers. And if we go deeper we see that the there are larger models, with a shell and tube, Plate, Adiabatic wheel, Plate Fin, Pillow plate, Fluid, Waste Heat Recovery units, Dynamic scraped surface, Phase-change heat exchangers, intermediate fluid or solid, and the ability to regenerate. Each of these is used for certain devices and can be found in almost all suppliers of heat exchanger. The heat exchanger is also so many types of heat and working with all different from each other, and is used in a wide variety of different devices

Monitoring and maintenance
Integrity inspection of plate and tubular heat exchanger can be tested in situ by the conductivity or helium gas methods. These methods confirm the integrity of the plates or tubes to prevent any cross contamination and the condition of the gaskets.Mechanical integrity monitoring of heat exchanger tubes may be conducted through Nondestructive methods such as eddy current testing
Fouling Fouling occurs when impurities deposit on the heat exchange surface. Deposition of these impurities can be caused by:- Low wall shear stress, Low fluid velocities, High fluid velocities, Reaction product solid precipitation, Precipitation of dissolved impurities due to elevated wall temperature.The rate of heat exchanger fouling is determined by the rate of particle deposition less re-entrainment/suppression.
Plate heat exchangers need to be disassembled and cleaned periodically. Tubular heat exchangers can be cleaned by such methods as acid cleaning, sandblasting, high-pressure water jet, bullet cleaning, or drill rods.In large-scale cooling water systems for heat exchangers, water treatment such as purification, addition of chemicals, and testing, is used to minimize fouling of the heat exchange equipment. Other water treatment is also used in steam systems for power plants, etc. to minimize fouling and corrosion of the heat exchange and other equipment.
A variety of companies have started using water borne oscillations technology to prevent biofouling. Without the use of chemicals, this type of technology has helped in providing a low-pressure drop in heat exchangers.

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<h1>Know More about Heat Exchanger</h1> Author: <a href='http://www.articleseen.com/profile_harry.aspx'>harry</a> A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, natural gas processing, and sewage treatment. 
How does it Work
A heat exchanger utilizes the fact that heat transfer occurs when there is a difference in temperature. 
In a heat exchanger, there is a cold stream and a hot stream. The two streams are separated by a thin, solid wall. The wall must be thin and conductive in order for heat exchange to occur. Yet the wall must be strong enough to withstand any pressure by fluid. Copper seems to be one of a common choice for construction
Flow Arrangement
There are two primary classifications of heat exchangers according to their flow arrangement. In parallel-flow heat exchangers, the two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side. In counter-flow heat exchangers the fluids enter the exchanger from opposite ends. The counter current design is most efficient.
Some ways to improve the performance of a heat exchanger: 
•	heat transfer area
•	fluid flow velocity
•	temperature gradient
There are a variety of designs and models of heat exchangers. And if we go deeper we see that the there are larger models, with a shell and tube, Plate, Adiabatic wheel, Plate Fin, Pillow plate, Fluid, Waste Heat Recovery units, Dynamic scraped surface, Phase-change heat exchangers, intermediate fluid or solid, and the ability to regenerate. Each of these is used for certain devices and can be found in almost all suppliers of heat exchanger. The heat exchanger is also so many types of heat and working with all different from each other, and is used in a wide variety of different devices

Monitoring and maintenance
Integrity inspection of plate and tubular heat exchanger can be tested in situ by the conductivity or helium gas methods. These methods confirm the integrity of the plates or tubes to prevent any cross contamination and the condition of the gaskets.Mechanical integrity monitoring of heat exchanger tubes may be conducted through Nondestructive methods such as eddy current testing
Fouling   Fouling occurs when impurities deposit on the heat exchange surface. Deposition of these impurities can be caused by:- Low wall shear stress, Low fluid velocities, High fluid velocities, Reaction product solid precipitation, Precipitation of dissolved impurities due to elevated wall temperature.The rate of heat exchanger fouling is determined by the rate of particle deposition less re-entrainment/suppression.
Plate heat exchangers need to be disassembled and cleaned periodically. Tubular heat exchangers can be cleaned by such methods as acid cleaning, sandblasting, high-pressure water jet, bullet cleaning, or drill rods.In large-scale cooling water systems for heat exchangers, water treatment such as purification, addition of chemicals, and testing, is used to minimize fouling of the heat exchange equipment. Other water treatment is also used in steam systems for power plants, etc. to minimize fouling and corrosion of the heat exchange and other equipment.
A variety of companies have started using water borne oscillations technology to prevent biofouling. Without the use of chemicals, this type of technology has helped in providing a low-pressure drop in heat exchangers.

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